Quote - They did release a 64 bit XP, a few years ago, but XP support is going to continue only for so much longer. It might be dropped by the end of 2010 or so.
It's up to you of course, which to get first, but you're definitely better off having both a 64 bit operating system as well as a quad core processor.
Personally I'd recommend waiting for Windows 7 official release, and not buy into Vista now. Then again, you could get Vista now and simply upgrade later, might save a little money that way.
Or you could download the Windows 7 RC 1 from Microsoft and use it for free until March of 2010 when it expires. That's what I did, and I don't regret it for a minute. I loved Vista, but Windows 7 is so much better in so many ways.

Waiting for Windows 7 makes no difference because Windows Vista comes with a free upgrade to Windows 7 now (which might be better in case I hate W7 anyway lol. Question though - is the free W7 version full of a lot of problems, and also, if I install Vista or that W7 now, do you have to reformat to install the OS? Because that's another thing I don't want to do it twice if you do.

Ok so still my main question - is Windows upgrade alone going to help with Poser speed at all? I know you need all the pieces but if I can only afford one I want to get what will make the most difference for me now. Or even if it would make more of a difference getting Poser 8 first (don't care about Pro I won't wait that long, plus don't even know if I need Pro)